In recent years, electronic tags, including RFID (Radio Frequency ID), have been popularized instead of such tags as bar codes. With the popularization of electronic tags, a method of attaching electronic tags to various articles and managing the articles has been proposed and realized.
One of the advantages of electronic tags is that bringing an electronic tag reader/writer close to an electronic tag causes them to communicate with each other by radio even if the reader/write is not brought into direct contact with the electronic tag, thereby enabling the information in the electronic tag (hereinafter, referred to as electronic tag information) to be read and written. Moreover, since electronic tags enable information to be read and written via radio communication, electronic tag information can be read from and written into a plurality of electronic tags at the same time. As described above, the exchange of information between an electronic tag and a tag reader/writer is carried out via radio communication. In addition, the tag reader/writer, when there are a plurality of electronic tags around it, may read electronic tag information from them simultaneously.
In such a case, it is difficult to determine from which electronic tag the read-out electronic tag information was read. In the case of bar codes, the reader is touched directly to the bar code of an article to be read, thereby reading the bar code, which enables the operator to check the bar-code-attached article. However, in the case of electronic tags, since the electronic tag information is read using radio communication, it may be impossible to determine from which electronic tag attached to an article the read-out electronic tag information was read. Moreover, even when there is only one type of electronic tag, if there are a plurality of articles and it is unknown which articles have electronic tags, it is impossible to determine which article the read-out electronic tag information is related to.